Surgical instrument for impacting and extracting a shaping instrument and a shaping instrument useable therewith

ABSTRACT

A surgical instrument including a shaping instrument for shaping a bone as well as an impaction/extraction device for use with the shaping instrument is disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending applicationSer. No. 13/309,140 filed Dec. 1, 2011, the entire disclosure of whichis hereby explicitly incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to surgical instruments, and, moreparticularly, to surgical instruments for preparing the proximal end ofa tibia for receiving a tibial prosthesis.

2. Description of the Related Art

Orthopaedic prostheses are commonly utilized to repair and/or replacedamaged bone and tissue in the human body. For example, a kneeprosthesis used in total knee arthroplasty may include a tibial baseplate that is affixed to a resected or natural proximal tibia, a femoralcomponent attached to a resected or natural distal femur, and a tibialbearing component coupled with the tibial base plate and disposedbetween the base plate and femoral component. Prostheses frequently seekto provide articulation similar to a natural, anatomic articulation of aknee joint, including providing a wide range of flexion.

To prepare the relevant bones of the human body to receive prostheticcomponents, a variety of shaping instruments are sometimes utilized. Inthe case of the proximal tibia, a bone saw may be utilized to prepare aplanar osteotomy of the proximal tibia which is then followed bydrilling of the intramedullary canal of the tibia to accommodate a stemextending from the base plate of a tibial prosthesis. Many tibialprostheses include a keel extending from opposing sides of the stem ofthe tibial prosthesis. To further shape the tibia to receive the tibialkeel, a broach is impacted into the proximal surface of the tibia tocreate a cavity sized to receive the keel of the tibial prosthesis.After impacting the broach, it must be extracted from the tibia whilemaintaining the shape of the cavity formed thereby. Similarly, acompaction instrument may be utilized to compact areas of bone to shapethe bone to receive the prosthesis. Compaction instruments must also beextracted from the bone while maintaining the shape of the cavity.

When preparing the proximal tibia to receive a tibial prosthesis,instrumentation including a sizing plate may be utilized to facilitateforming a cavity in the tibia sized and shaped to accommodate the stemand keel of a tibial prosthesis that is properly positioned andoriented. The size of the sizing plate corresponds to the size of aprosthesis which is to be mated to the bone. The sizing plate ispositioned atop the proximal tibia after the initial, planar osteotomyis performed. Positioning of the sizing plate provides an indication ofthe location and orientation of the final prosthesis and guides thelocation of the subsequent bone shaping steps, e.g., drilling, broachingand compacting, which are utilized to prepare the bone to receive thetibial prosthesis.

SUMMARY

The present disclosure provides a surgical instrument including ashaping instrument for shaping a bone as well as an impaction/extractiondevice for use with the shaping instrument. The impaction/extractiondevice includes a housing having an internal wall defining alongitudinal cannula and a central shaft positioned in the longitudinalcannula of the housing. The central shaft is moveable longitudinallywithin the longitudinal cannula of the housing. The central shaft issecured or releasably securable to the shaping instrument so thatreciprocation of the central shaft within the housing can cause theshaping instrument to, alternatively, be impacted into or extracted froma bone. An extraction lever is pivotally connected to the housing andpresents a proximally facing impaction surface adjacent to an impactionsurface formed on a proximal end of the central shaft. The impactionsurface formed on the proximal end of the central shaft is alsoproximally facing. With this configuration, impaction of the impactionsurface of the central shaft as well as impaction of the impactionsurface of the extraction lever can be done by impacting or strikingthese surfaces with a mallet in a proximal to distal motion. Theextraction lever includes an extraction arm opposite the extractionlever and impaction surface, with the extraction arm positionable intocontact with a distal facing extraction surface formed on the centralshaft. In this configuration, impaction of the extraction leverimpaction surface positions the extraction arm in contact with theextraction surface of the central shaft and applies a distal to proximalforce to the central shaft to effect extraction of a shaping instrumentwhich has previously been impacted into the tibia.

The extraction lever impaction surface may be curved to facilitateimpaction of the same with a mallet moving in a proximal to distaldirection relative to the instrument. Specifically, as the extractionlever articulates to effect extraction of the shaping instrument fromthe bone, the curved surface ensures that no matter the rotationalposition of the extraction lever, the extraction lever impaction surfacepresents a proximally facing surface transverse to the longitudinal axisof the central shaft. Specifically, the extraction lever impactionsurface of this form of the present invention defines a curve in a planecontaining the longitudinal axis of the central shaft and issubstantially linear in a direction perpendicular to that plane. For thepurposes of this description, substantially linear is meant to encompassdeviations from linear within manufacturing tolerances. With respect tothe surgical instrument of the present disclosure, “proximal” and“distal” are used with reference to a user of the instrument.Specifically, “proximal” denotes a position of the instrument closest toa user of the instrument, while “distal” refers to a portion of theinstrument furthest from the user during use of the instrument.

When used in combination with a support structure such as a tibialsizing plate, the surgical instrument of the present invention mayincorporate at least one magnet positioned to attract the supportstructure to the housing of the surgical instrument as the supportstructure is indexed to the surgical instrument. Embodiments of thesurgical instrument of the present invention may further include a balldetent or spring clip operable to hold the central shaft in a retractedposition relative to the housing. The ball detent of this form of thepresent invention is useful in retracting the shaping instrument fromthe distal extent of the housing so that the surgical instrument can besecured to a support structure without interference from the shapinginstrument.

The shaping instrument of certain embodiments of the present disclosuremay include a ramp feature to facilitate simplified securement of theshaping instrument to an impaction/extraction instrument of the presentdisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a perspective view of a surgical instrument in accordance withthe present invention;

FIG. 2 is a radial elevational view of impaction/extraction instrumentin accordance with the present invention;

FIG. 3 is a cross-sectional view of the instrument illustrated in FIGS.1 and 2 taken along lines 3-3 of FIG. 1;

FIG. 4 is a partial view of the impaction/extraction instrumentillustrated in FIGS. 1-3, illustrating use of the same to impact ashaping instrument;

FIG. 5 is a partial view of the impaction/extraction instrumentillustrated in FIGS. 1-3, illustrating use of the same to extract ashaping instrument;

FIG. 6 is a perspective view of a tibial sizing plate useable to guidethe impaction/extraction instrument of the present invention;

FIG. 7 is a sectional view illustrating a magnetic securement mechanismin accordance with the present invention;

FIG. 8 is a perspective view of an alternative embodiment tibial broachin accordance with the present disclosure;

FIG. 9 is a sectional view of the tibial broach of FIG. 8 taken alongmidline 9-9 of FIG. 8;

FIG. 10 is a perspective view of another alternative embodiment tibialbroach in accordance with the present disclosure;

FIG. 11 is a perspective view of yet another alternative embodimenttibial broach in accordance with the present disclosure; and

FIGS. 12-14 are partial sectional views illustrating securement of thetibial broach of FIG. 8 to the impaction/extraction instrumentillustrated in FIGS. 1-3.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereindescribe and illustrate exemplary embodiments of the invention, and suchexemplifications are not to be construed as limiting the scope of theinvention in any manner.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, impaction/extraction instrument 10 includeshousing 12 and central shaft 14. Referring to FIG. 3, housing 12includes internal wall 16 defining a longitudinal cannula spanningproximal end 18 and distal end 20 of housing 12. As illustrated in FIG.3, central shaft 14 is positioned within the cannula formed by internalwall 16. Internal wall 16 of housing 12 and the exterior of centralshaft 14 have complementary geometries, e.g., circular geometries, whichallow for axial reciprocation of central shaft 14 along its longitudinalaxis L relative to housing 12. Tibial broach 24 is secured to a distalend of central shaft 14. The exemplary embodiments of the presentdisclosure described below make reference to the use ofimpaction/extraction instrument 10 with various embodiments of a tibialbroach. This description is but one exemplification of the use ofimpaction/extraction instrument 10, which is usable with any shapinginstrument that is impacted into and subsequently extracted from ananatomic structure, including any cutting and/or compacting instrument.

Referring to FIGS. 2 and 3, central shaft 14 includes internal wall 22defining a T-shaped recess at a distal end of central shaft 14. Asillustrated in FIG. 3, internal wall 22 of central shaft 14 extendsperpendicular to longitudinal axis L of central shaft 14 such that theT-shaped recess formed by internal wall 22 of central shaft 14 isperpendicular to the longitudinal axis L of central shaft 14. Referringto FIG. 2, tibial broach 24 includes T-shaped protrusion 26 at aproximal end thereon. T-shaped protrusion 26 has a complimentarygeometry to the geometry of the T-shaped recess formed by internal wall22 of central shaft 14. Specifically, T-shaped protrusion 26 issubstantially congruent to the T-shaped recess formed by internal wall22 of central shaft 14 and is sized such that a close fit can be formedtherebetween. Referring to FIG. 3, central shaft 14 includeslongitudinal bore 28 which is intersected by transverse bore 30.Longitudinal bore 28 is sized to receive locating pin 32 as well asspring 34. As illustrated in FIG. 3, longitudinal bore 28 is exemplifiedas a stepped bore having a smaller diameter portion receiving spring 34and a larger diameter portion receiving locating pin 32. Locating pin 32includes proximal protrusion 36 which terminates distally at shoulder38. Proximal protrusion 36 is sized to be received within the interiorof spring 34. Shoulder 38 has a radial expanse greater than the radialexpanse of spring 34 so that spring 34 rests against shoulder 38.Locating pin 32 includes transverse bore 40 into which button 42 ispositioned. Button 42 is secured to locating pin 32 so that movement ofbutton 42 effects movement of locating pin 32. As illustrated in FIG. 3,spring 34 biases locating pin 32 distally such that button 42 abuts thedistal portion of the wall forming transverse bore 30.

At its distal end, locating pin 32 includes spherical distal end 44. Asillustrated in FIG. 3, spherical distal end 44 projects into theT-shaped recess defined by internal wall 22 of central shaft 14 in thenormally biased position of locating pin 32. Spherical end 44 oflocating pin 32 may be withdrawn from the T-shaped recess formed byinternal wall 22 of central shaft 14 by actuating button 42 proximallyso that locating pin 32 is moved against the spring biasing force ofspring 34.

In one embodiment, to operably secure tibial broach 24 toimpaction/extraction instrument 10, button 42 is actuated proximallyagainst the spring biasing force of spring 34 to withdraw sphericaldistal end 44 of locating pin 32 from the T-shaped recess defined byinternal wall 22 of central shaft 14. With spherical distal end 44 oflocating pin 32 withdrawn from the T-shaped recess, T-shaped protrusion26 of tibial broach 24 can be positioned within the T-shaped recessformed by internal wall 22 of central shaft 14. In this position,actuation of button 42 may cease so that spring 34 biases locating pin32 downwardly and spherical distal end 44 of locating pin 32 ispositioned within divot 46 formed in a proximal end of tibial broach 24.

Alternative embodiments of tibial broach 24 are illustrated in FIGS.8-14. These alternative embodiments include many features in common withtibial broach 24 illustrated in FIGS. 1-3. Similar features of thevarious tibial broach embodiments disclosed herein are denoted withsimilar reference numerals followed by a differing alphabeticdesignation. Referring to FIGS. 8 and 9, tibial broach 24 a includesT-shaped protrusion 26 a having divot 46 a formed therein. Tibial broach24 a further includes ramp 100 a formed on a leading end of protrusion26 a. As illustrated in FIGS. 8 and 9, broach ramp 100 is formed by alead in chamfer forming an angle α relative to longitudinal axis L oftibial broach 24. In one exemplary embodiment, α is 50°. In alternativeembodiments, a can be any angle in the range of 30-60°.

FIGS. 12-14 illustrate securement of tibial broach 24 a toimpaction/extraction instrument 10. In this embodiment, it isunnecessary to actuate button 42 to secure tibial broach 24 a toimpaction/extraction instrument 10. As illustrated in FIG. 12,securement of tibial broach 24 a to impaction/extraction instrument 10begins by positioning T-shaped protrusion 26 of tibial broach 24 inalignment with the T-shaped recess defined by internal wall 22 ofcentral shaft 14. In this position, force F (FIG. 13) urges T-shapedprotrusion 26 a of tibial broach 24 a into the T-shaped recess definedby internal wall 22 of central shaft 14 until ramp 100 a abuts thedistal end of locating pin 32. From this position, further movement oftibial broach 24 a in the direction of force F causes locating pin 32 toride along ramp 100 a and move against the biasing force of spring 34.After the distal end of locating pin 32 fully traverses ramp 100 a,additional movement of tibial broach 24 a in the direction of force Fpositions divot 46 a in alignment with locating pin 32 so that thebiasing force of spring 34 causes locating pin 32 to occupy divot 46 aas illustrated in FIG. 14. Advantageously, this alternative embodimentof the present invention simplifies the procedure for securing a tibialbroach to the impaction/extraction instrument and allows for “onehanded” assembly of the tibial broach to the impaction/extractioninstrument. While described with respect to a locating pin, alternativelocating features such as a ball detent may be utilized to secure abroach of a present disclosure to an impaction/extraction instrument ofthe present disclosure. Similarly, while the simplified securementfeature of the present disclosure has been described with reference to atibial broach, it may be incorporated into any shaping instrument thatis secured to an impaction/extraction instrument.

FIGS. 10 and 11 illustrate further alternative tibial broaches which maybe assembled to impaction/extraction instrument 10 in the same fashionthat tibial broach 24 a is secured to impaction/extraction instrument10. Referring to FIG. 10, tibial broach 24 b includes ramp 100 b formedby a v-shaped lead in groove. Flanking sides of ramp 100 b are angled toconverge as they move away from the leading end of protrusion 26 b. Incertain embodiments, the apex of this v-shaped groove is rounded to atransverse radius closely approximating the radius of a spherical distalend of locating pin 32.

Referring to FIG. 11, tibial broach 24 c includes ramp 100 c in the formof a spherical groove. In this embodiment, ramp 100 c may be formed by,e.g., a 12 mm diameter ball end mill. Both ramp 100 b and ramp 100 cdefine a path through a transverse cross-section through the midline ofthe respective tibial broach (such a cross-section of tibial broach 24 ais illustrated in FIG. 9) which forms an angle a as previously describedwith respect to tibial broach 24 a. Specifically, the angle a formed bythe inner most surface of ramps 100 b and 100 c taken through a midlineof the respective tibial broach forms an angle with the longitudinalaxis of the tibial broach having a quantity anywhere in the range of30-60°. In exemplary embodiments, this angle is 50°.

With tibial broach 24 secured to impaction/extraction instrument 10, thecentral shaft 14 can be pulled proximally relative to housing 12 to movetibial broach 24 proximally relative to housing 12 such that distal end48 of tibial broach 24 does not extend distally from distal end 20 ofhousing 12. In this way, the distal most extent of tibial broach 24 willnot extend beyond the distal most extent of housing 12 and, therefore,securement of impaction/extraction instrument 10 to a support structure,as will be further described hereinbelow, will not be interfered with bytibial broach 24. To hold tibial broach 24 in this retracted position,central shaft 14 includes divot 50 sized to receive ball 52 of a balldetent mechanism. As illustrated in FIG. 3, divot 50 can take the formof an annular groove extending about the circumference of central shaft14. With tibial broach 24 in the withdrawn position, ball 52 engagesdivot 50 to hold tibial broach in a position such that it does notextend beyond distal end 20 of housing 12. Divot 50 may, in alternativeembodiments, comprise a spherical divot sized to receive ball 52. Tomove tibial broach 24 from this position, impaction surface 54 may beimpacted by mallet 56 (FIG. 1).

The ball detent mechanism utilized to hold tibial broach 24 in itswithdrawn position includes transverse bore 58 intersecting internalwall 16 at opening 60. Opening 60 can be a circular opening having adiameter less than the diameter of ball 52. Positioned within transversebore 58 is spring 62 and set screw 64. In an alternative embodiment, setscrew 64 may be replaced with a cap which is welded in place withintransverse bore 58. In the finally seated position of set screw 64illustrated in FIG. 3, spring 62 is compressed against ball 52 such thatball 52 extends beyond opening 60 and into the longitudinal cannuladefined by internal wall 16 of housing 12. As central shaft 14 is movedproximally, ramp 66 formed on central shaft 14 engages ball 52 so thatball 52 is moved against the biasing force of spring 62 and withdrawnfrom the cannula defined by internal wall 16 of housing 12. As centralshaft 14 is moved further proximally such that ball 52 is aligned withdivot 50, biasing force of spring 62 positions ball 52 in divot 50 asdescribed hereinabove. The retracted position of tibial broach 24 isillustrated in FIG. 1.

A position of tibial broach 24 corresponding to its maximum extensiondistally from distal end 20 of housing 12 is illustrated in FIGS. 2 and3. In this position, extraction lever 68 can be utilized to apply adistal to proximal force to central shaft 14 and move central shaft 14and tibial broach 24 proximally. Extraction lever 68 is pivotallyconnected to housing 12 by cylindrical pivot pin 70. Cylindrical pivotpin 70 is pivotally received in a pivot aperture sized to allow rotationbut not radial translation of cylindrical pivot pin 70 relative to thepivot aperture. In the embodiment illustrated in FIG. 3, extractionlever 68 includes cylindrical aperture 72 into which cylindrical pivotpin 70 is positioned. In this embodiment, cylindrical aperture 72 issized to receive cylindrical pivot pin 70 to pivotally connectextraction lever 68 to housing 12, with cylindrical aperture 72 sized toallow rotation of extraction lever 68 relative to housing 12 but not toallow translation of extraction lever 68 in a direction orientedradially from cylindrical pivot pin 70. In alternative embodiments,cylindrical pivot pin 70 may be fixedly secured to extraction lever 68but may be pivotally connected within a cylindrical aperture formed inyolk 84 (FIG. 1) in a similar fashion to the pivotal connection betweencylindrical pivot pin 70 and cylindrical aperture 72 described above.

On opposing sides of cylindrical pivot pin 70, extraction lever 68includes extraction lever impaction surface 74 and extraction arm 76.Extraction lever impaction surface 74 faces proximally, away from distalend 20 of housing 12. Because extraction lever impaction surface 74faces proximally, it can be impacted by mallet 56 (FIG. 1) along atrajectory parallel to the impaction required to seat tibial broach 24,as will be further described hereinbelow.

Extraction arm 76 resides within slot 78 formed in central shaft 14. Asillustrated in FIG. 3, slot 78 terminates proximally in extractionsurface 80. Extraction surface 80 faces distally, away from impactionsurface 54 which forms the proximal end of impaction/extractioninstrument 10. With this arrangement, impaction of extraction leverimpaction surface 74 with mallet 56 positions extraction arm 76 tocontact extraction surface 80 and apply a distal to proximal force tocentral shaft 14 which will tend to pull tibial broach 24 proximallyfrom the position illustrated in FIG. 3 toward the withdrawn positionillustrated in FIG. 1. Movement of extraction arm 76 relative to housing12 is accommodated by slot 82 formed in housing 12.

Referring to FIG. 3, extraction lever impaction surface 74 has aradially outward most extent relative to longitudinal axis L of centralshaft 14 illustrated as distance D. Distance D measures no more than 10cm. With extraction lever impaction surface 74 spaced no more than 10 cmfrom longitudinal axis L of central shaft 14, the torque imparted toimpaction/extraction instrument 10 when mallet 56 strikes extractionlever impaction surface is minimized and therefore toggling of tibialbroach 24 within the broached bone will be minimized. Furthermore, thecenter of impaction surface 74 is spaced approximately 25 mm from thecenter of cylindrical pivot pin 70. With an expected impaction force onthe extraction head of approximately 7 kN, this would result in a torqueabout the center of cylindrical pivot pin 70 of about (7,000 N)×(0.025m)=175 Nm. The inventors of the present invention have concluded that atorque of less than 300 Nm is desired to prevent toggling of tibialbroach 24 during extraction thereof In certain embodiments of thepresent invention, distance D can be as little as 5 cm. In alternativeembodiments of the present invention, distance D can be any valuebetween 5 and 10 cm in 0.5 cm increments, i.e., 5.0, 5.5, 6.0, 6.5, 7.0,7.5, 8.0, 8.5, 9.0, 9.5 or 10.0 cm.

In an exemplary embodiment of the present invention, the lever ratio ofthe extraction lever is approximately 1.6:1. What this means is that thelength of the arm extending from the center of cylindrical pivot pin 70to a terminal end of extraction lever 68 adjacent to extraction leverimpaction surface 74 is approximately 1.6 times the length of extractionarm 76 from the center of cylindrical pivot pin 70 to a second terminalend of extraction lever 68 on extraction arm 76. The inventors of thepresent application have determined that a lever ratio of extractionlever 68 anywhere between 3:1 to 1:1 strikes an appropriate balancebetween decreasing toggling of tibial broach 24 during extraction whilealso providing an instrument actuateable with a comfortable amount offorce applied by the user.

Extraction lever impaction surface 74 defines a curve in a planecontaining the longitudinal axis of central shaft 14. The section planealong which FIG. 3 is taken is such a plane. As illustrated in FIG. 3,extraction lever impaction surface 74 is curved in a plane containinglongitudinal axis L of central shaft 14. While extraction leverimpaction surface 74 is curved in a plane containing longitudinal axis Lof central shaft 14, it is substantially linear in a directionperpendicular to such plane. “Substantially linear” is meant toencompass linear configurations and those configurations withinmanufacturing tolerances of being linear. What this means is that inplanes parallel to the plane along which the cross-sectional view ofFIG. 3 is taken, the profile of extraction lever impaction surface 74remains unchanged. Curving of extraction lever impaction surface 74facilitates articulation of extraction lever 68 by impacting extractionlever impaction surface 74 with mallet 56. Specifically, the curvatureof extraction lever impaction surface 74 means that mallet 56 can beactuated in a proximal to distal direction d as illustrated in FIG. 5while maintaining good contact with extraction lever impaction surface74 throughout a full range of motion of extraction lever 68.

Referring to FIG. 1, impaction/extraction instrument 10 can be utilizedto broach tibia T in the following manner. After initially osteotomizingproximal surface P of tibia T, tibial sizing plate 86 is chosen,oriented with respect to tibial T and secured thereto. Techniques forosteotomizing proximal surface P of tibia T can include securing a cutguide to tibia T which guides an oscillating saw to cut proximal tibiaT. Examples of such techniques can be found in the Zimmer NexGen LPSFixed Knee Surgical Technique bearing copyright dates of 2002, 2008, theentire disclosure of which is hereby explicitly incorporated byreference herein. Alternative techniques for osteotomizing the proximaltibia and utilizing a sizing plate can be found in the Zimmer NexGen CRFlex and LPS Flex Knees Surgical Technique with posterior referencinginstrumentation bearing copyright dates of 2010, 2011 and the ZimmerNexGen MIS Tibial Component Cemented Surgical Technique bearingcopyright dates of 2005, 2006, 2008, 2009 and 2010, the entiredisclosures of which are hereby explicitly incorporated by referenceherein. Additionally, preparation of a tibia to receive a tibialprosthesis is shown and described in U.S. Pat. No. 5,634,927, assignedto the assignee of the present disclosure, the entire disclosure ofwhich is hereby explicitly incorporated by reference herein.

After pinning tibial sizing plate 86 to tibia T, impaction/extractioninstrument 10 can be indexed to tibial sizing plate 86 so thatimpaction/extraction instrument 10 is supported and guided by tibialsizing plate 86. Referring to FIGS. 2 and 7, impaction/extractioninstrument 10 includes bosses 88 extending distally from distal ends 20of housing 12. Bosses 88 are sized, shaped and spaced to cooperate withapertures 90 (FIG. 6) in tibial sizing plate 86 to indeximpaction/extraction instrument 10 to tibial sizing plate 86. In aportion of housing 12 adjacent to each boss 88, a chamber holds a magnet92 as illustrated in FIG. 7. Magnets 92 are oriented relative to theirrespective bosses 88 such that when each boss 88 is positioned within anaperture 90 to index impaction/extraction instrument 10 to tibial sizingplate 86, magnet 92 will be positioned over a proximal surface of tibialbase plate 86. When using a metallic base plate 86, magnets 92 will drawtibial sizing plate 86 toward impaction/extraction instrument 10 andfacilitate indexing of impaction/extraction instrument 10 to tibialsizing plate 86. During this process of indexing impaction/extractioninstrument 10 to tibial sizing plate 86, tibial broach 24 can maintainthe extracted position illustrated in FIG. 1 so that it cannot interferewith the indexing process.

With impaction/extraction instrument 10 properly indexed to tibialsizing plate 86, mallet 56 may be utilized to strike impaction surface54 to seat tibial broach 24 in tibia T and create an aperture in tibia Tsized to accommodate the keel of a tibial prosthesis. Specifically,while using one hand to grasp housing 12, a surgeon may use his or herother hand to actuate mallet 56 so that its head collides with impactionsurface 54 to impact the impaction surface and effect seating of tibialbroach 24 in tibia T. Prior to broaching tibia T, aperture 94 may beformed in tibia T to accommodate distal end 48 of tibial broach 24. Asdistal end 48 of tibial broach 24 enters aperture 94, teeth 96 of tibialbroach 24 contact the bone of tibia T and effect cutting of the same.Final seating of tibial broach 24 is signaled when undersurface 98opposing impaction surface 54 contacts proximal end 18 of housing 12 asillustrated in FIGS. 3 and 4. In this position, mallet 56 may beutilized to provide an impaction force to extraction lever impactionsurface 74 as illustrated in FIG. 5. Such impaction force creates atorque about the center of cylindrical pivot pin 70 (FIG. 3) andgenerates an extraction force in a distal to proximal direction alonglongitudinal axis L of central shaft 14.

While this invention has been described as having an exemplary design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A surgical instrument, comprising: a shaping instrument for shaping a bone; a housing having an internal wall defining a longitudinal cannula; a central shaft positioned in said longitudinal cannula of said housing, said central shaft having a longitudinal axis, said central shaft moveable within said longitudinal cannula of said housing relative to said housing along said longitudinal axis of said central shaft, said central shaft having a proximal end and a distal end securable to said shaping instrument; an impaction surface facing proximally, away from a distal end of the surgical instrument, said impaction surface forming said proximal end of said central shaft, whereby impacting said impaction surface applies a proximal to distal force to said central shaft; an extraction lever pivotally connected to said housing, said extraction lever having an extraction lever impaction surface facing proximally, away from the distal end of the surgical instrument, said extraction lever impaction surface moveable relative to said central shaft, said extraction lever having an extraction arm opposite said extraction lever impaction surface, said central shaft having an extraction surface facing distally away from a proximal end of the surgical instrument, said extraction arm positionable to contact said extraction surface, whereby impacting said extraction lever impaction surface positions said extraction arm in contact with said extraction surface and applies a distal to proximal force to said central shaft.
 2. The surgical instrument of claim 1, wherein said extraction lever impaction surface defines a curve in a plane containing the longitudinal axis of the central shaft, said impaction surface being substantially linear in a direction perpendicular to said plane.
 3. A combination, comprising the surgical instrument of claim 1 and a metallic support structure having a support structure indexing feature, said housing having a housing indexing feature, said support structure indexing feature and said housing indexing feature selectably engageable to index the surgical instrument to the support structure, said housing incorporating at least one magnet positioned to attract said metallic support structure to said housing as said housing indexing feature in brought into engagement with said support structure indexing feature.
 4. The combination of claim 3, wherein said metallic support structure comprises a tibial sizing plate and wherein said shaping instrument comprises a tibial broach.
 5. The surgical instrument of claim 1, wherein said housing includes a transverse bore intersecting said longitudinal cannula of said housing at an opening, said surgical instrument further comprising: a ball detent positioned in said transverse bore and extending into said longitudinal cannula of said housing, said ball detent having a diameter larger than a diameter of said opening; a spring positioned in said transverse bore and biasing said ball detent toward said opening; said central shaft including a divot sized to receive said ball detent, whereby, with said ball detent positioned in said divot, movement of said central shaft relative to said housing is resisted, whereby, with said shaping instrument secured to said central shaft and with said ball detent positioned in said divot, said shaping instrument does not extend distally beyond a distal extent of said housing.
 6. The surgical instrument of claim 1, wherein said extraction lever impaction surface is spaced no more than 10 cm from said longitudinal axis of said central shaft.
 7. The surgical instrument of claim 1, further comprising: a cylindrical pivot pin pivotally received in a pivot aperture sized to allow rotation but not radial translation of said cylindrical pivot pin relative to said pivot aperture, said cylindrical pivot pin pivotally connecting said extraction lever to said housing.
 8. The surgical instrument of claim 7, wherein said extraction lever extends a first distance from a center of said cylindrical pivot pin to a first terminal end of the extraction lever adjacent to the extraction lever impaction surface and said extraction lever extends a second distance from said center of said cylindrical pivot pin to a second terminal end of the extraction lever on the extraction arm, a ratio of said first distance to said second distance being in a range of 3:1 to 1:1.
 9. The surgical instrument of claim 8, wherein said ratio of said first distance to said second distance equals 1.6:1.
 10. The surgical instrument of claim 1, wherein said distal end of said central shaft includes a central shaft securement feature, said shaping instrument including a shaping instrument securement feature matable with said central shaft securement feature to releasably secure said shaping instrument to said central shaft.
 11. The surgical instrument of claim 10, wherein said central shaft securement feature comprises a wall defining a T-shaped recess and a locating pin having a spherical distal end, said locating pin moveable within said T-shaped recess, and said shaping instrument securement feature comprises a T-shaped protrusion shaped to be received within said T-shaped recess of said central shaft and a divot sized to receive said spherical distal end of said locating pin, whereby, with said T-shaped protrusion positioned in said T-shaped recess and said spherical distal end of said locating pin positioned in said divot, movement of said shaping instrument relative to said central shaft is resisted.
 12. The surgical instrument of claim 1, wherein said distal end of said central shaft comprises a wall forming a transverse recess, said transverse recess extending transverse to said longitudinal axis of said central shaft, said surgical instrument further comprising a locating feature, said central shaft further comprising a longitudinal bore intersecting said transverse recess, said locating feature moveably positioned in said longitudinal bore and biased to a biased position to extend from said longitudinal bore into said transverse recess, said shaping instrument comprising a protrusion sized to be received in said transverse recess of said central shaft and a divot formed in said protrusion of said shaping instrument, said divot sized to receive said locating feature, whereby, with said protrusion positioned in said transverse recess and said locating feature positioned in said divot, movement of said shaping instrument relative to said central shaft is resisted, said protrusion of said shaping instrument including a ramp positioned to contact said locating feature when said protrusion of said shaping instrument is positioned in said transverse recess, whereby movement of said shaping instrument transverse to the longitudinal axis of the central shaft with the locating feature positioned against the ramp causes the locating feature to ride along the ramp and be displaced from said biased position, said locating feature biased into said divot in said shaping instrument after traversing said ramp.
 13. The surgical instrument of claim 12, wherein the locating feature comprises a locating pin.
 14. The surgical instrument of claim 12, wherein said ramp comprises a chamfer forming an angle in a range of 30-60° with a longitudinal axis of said shaping instrument.
 15. The surgical instrument of claim 12, wherein said ramp comprises a v-shaped groove.
 16. The surgical instrument of claim 12, wherein said ramp comprises a spherical groove.
 17. A surgical instrument, comprising: a shaping instrument for shaping a bone; a housing having an internal wall defining a longitudinal cannula; a central shaft positioned in said longitudinal cannula of said housing, said central shaft having a longitudinal axis, said central shaft moveable within said longitudinal cannula of said housing relative to said housing along said longitudinal axis of said central shaft, said central shaft having a proximal end and a distal end securable to said shaping instrument; an impaction surface facing proximally, away from a distal end of the surgical instrument, said impaction surface forming said proximal end of said central shaft, whereby impacting said impaction surface applies a proximal to distal force to said central shaft; an extraction lever pivotally connected to said housing, said extraction lever having an extraction lever impaction surface facing proximally away from the distal end of the surgical instrument, said extraction lever impaction surface defining a curve in a plane containing the longitudinal axis of the central shaft, said impaction surface being substantially linear in a direction perpendicular to said plane, said extraction lever having an extraction arm opposite said extraction lever impaction surface, said central shaft having an extraction surface facing distally, away from a proximal end of the surgical instrument, said extraction arm positionable to contact said extraction surface, whereby impacting said extraction lever impaction surface positions said extraction arm in contact with said extraction surface and applies a distal to proximal force to said central shaft.
 18. A combination, comprising the surgical instrument of claim 17 and a metallic support structure having a support structure indexing feature, said housing having a housing indexing feature, said support structure indexing feature and said housing indexing feature selectably engageable to index the surgical instrument to the support structure, said housing incorporating at least one magnet positioned to attract said metallic support structure to said housing as said housing indexing feature in brought into engagement with said support structure indexing feature.
 19. The combination of claim 18, wherein said support structure comprises a tibial sizing plate and wherein said shaping instrument comprises a tibial broach.
 20. The surgical instrument of claim 17, wherein said housing includes a transverse bore intersecting said longitudinal cannula of said housing at an opening, said surgical instrument further comprising: a ball detent positioned in said transverse bore and extending into said longitudinal cannula of said housing, said ball detent having a diameter larger than a diameter of said opening; a spring positioned in said transverse bore and biasing said ball detent toward said opening; said central shaft including a divot sized to receive said ball detent, whereby, with said ball detent positioned in said divot, movement of said central shaft relative to said housing is resisted, whereby, with said shaping instrument secured to said central shaft and with said ball detent positioned in said divot, said shaping instrument does not extend distally beyond a distal extent of said housing.
 21. The surgical instrument of claim 17, wherein said extraction lever impaction surface is spaced no more than 10 cm from said longitudinal axis of said central shaft.
 22. The surgical instrument of claim 17, further comprising: a cylindrical pivot pin pivotally received in a pivot aperture sized to allow rotation but not radial translation of said cylindrical pivot pin relative to said pivot aperture, said cylindrical pivot pin pivotally connecting said extraction lever to said housing.
 23. The surgical instrument of claim 22, wherein said extraction lever extends a first distance from a center of said cylindrical pivot pin to a first terminal end of the extraction lever adjacent to the extraction lever impaction surface and said extraction lever extends a second distance from said center of said cylindrical pivot pin to a second terminal end of the extraction lever on the extraction arm, a ratio of said first distance to said second distance being in a range of 3:1 to 1:1.
 24. The surgical instrument of claim 23, wherein said ratio of said first distance to said second distance equals 1.6:1.
 25. The surgical instrument of claim 17, wherein said distal end of said central shaft comprises a wall forming a transverse recess, said transverse recess extending transverse to said longitudinal axis of said central shaft, said surgical instrument further comprising a locating feature, said central shaft further comprising a longitudinal bore intersecting said transverse recess, said locating feature moveably positioned in said longitudinal bore and biased to a biased position to extend from said longitudinal bore into said transverse recess, said shaping instrument comprising a protrusion sized to be received in said transverse recess of said central shaft and a divot formed in said protrusion of said shaping instrument, said divot sized to receive said locating feature, whereby, with said protrusion positioned in said transverse recess and said locating feature positioned in said divot, movement of said shaping instrument relative to said central shaft is resisted, said protrusion of said shaping instrument including a ramp positioned to contact said locating feature when said protrusion of said shaping instrument is positioned in said transverse recess, whereby movement of said shaping instrument transverse to the longitudinal axis of the central shaft with the locating feature positioned against the ramp causes the locating feature to ride along the ramp and be displaced from said biased position, said locating feature biased into said divot in said shaping instrument after traversing said ramp.
 26. The surgical instrument of claim 25, wherein the locating feature comprises a locating pin.
 27. The surgical instrument of claim 25, wherein said ramp comprises a chamfer forming an angle in a range of 30-60° with a longitudinal axis of said shaping instrument.
 28. The surgical instrument of claim 25, wherein said ramp comprises a v-shaped groove.
 29. The surgical instrument of claim 25, wherein said ramp comprises a spherical groove.
 30. A method of shaping a bone to receive a prosthetic component, comprising the steps of: providing a shaping instrument; providing an impaction/extraction instrument having a distal end and a proximal end, the proximal end having an impaction surface, the impaction surface facing proximally away from the distal end of the impaction/extraction instrument, the impaction/extraction instrument having an extraction surface facing proximally away from the distal end of the impaction/extraction instrument; securing said shaping instrument to said distal end of the impaction/extraction instrument; impacting the impaction surface to seat the shaping instrument in the bone by applying a proximal to distal force to the impaction surface; and impacting the extraction surface to unseat the shaping instrument from the bone by applying a proximal to distal force to the extraction surface.
 31. The method of claim 30, wherein the impaction/extraction instrument comprises a housing having an internal wall defining a longitudinal cannula and a central shaft positioned in the longitudinal cannula of the housing, the central shaft having a longitudinal axis, the central shaft moveable within the longitudinal cannula of the housing relative to the housing along the longitudinal axis of the central shaft, the impaction surface of the impaction/extraction instrument formed on a central shaft proximal end, the central shaft having a central shaft distal end securable to the shaping instrument, the central shaft distal end comprising a wall forming a transverse recess, the transverse recess extending transverse to the longitudinal axis of the central shaft, the impaction/extraction instrument further comprising a locating feature, said central shaft further comprising a longitudinal bore intersecting the transverse recess, the locating feature moveably positioned in the longitudinal bore and biased to a biased position to extend from the longitudinal bore into the transverse recess, the shaping instrument comprising a protrusion sized to be received in the transverse recess of the central shaft and a divot formed in the protrusion of the shaping instrument, the divot sized to receive the locating feature, whereby with the protrusion positioned in the transverse recess and the locating feature positioned in the divot, movement of the shaping instrument relative to the central shaft is resisted, the protrusion of the shaping instrument including a ramp positioned to contact the locating feature when the protrusion of the shaping instrument is positioned in the transverse recess, wherein said step of securing said shaping instrument to said distal end of the impaction/extraction instrument comprises: positioning the protrusion of the shaping instrument in the transverse recess of the central shaft to position the locating feature against the ramp; moving the shaping instrument so that the locating feature rides along the ramp and is displaced from the biased position, until the locating feature fully traverses the ramp and is biased into the divot in the shaping instrument.
 32. The method of claim 30, further comprising the steps of: providing a metallic support structure; indexing the impaction/extraction instrument to the support structure, the impaction/extraction instrument having a magnet disposed adjacent to the distal end, the magnet drawing the metallic support structure into engagement with the impaction/extraction instrument during said indexing step.
 33. The method of claim 32, further comprising the steps of: withdrawing the shaping instrument into a withdrawn position so that it does not extend distally from the distal end of the impaction/extraction instrument; and holding the shaping instrument in the withdrawn position during said step of indexing the impaction/extraction instrument to the support structure. 